In the railroad industry, draft gear assemblies of the friction-type have been in widespread use on rolling stock for many years. Such draft gear assemblies are used to absorb both the buff and draft shocks applied to the railroad rolling stock during normal operation. See, for example, U.S. Pat. Nos. 2,916,163; 3,178,036; 3,447,693; 4,576,295; 4,645,187 and 4,735,328 for a teaching of a number of draft gear assemblies which were in use in the railway industry prior to the present invention. Except for U.S. Pat. Nos. 4,576,295 and 4,735,328, each of the remaining above-identified patents is owned by the assignee of the present invention. The teachings of all of the above-identified prior art patents are incorporated into the present application by reference thereto.
It is well recognized, by persons skilled in the draft gear art, that these draft gear assemblies must maintain certain minimum shock absorbing capacity during in-track service. This minimum shock absorbing capacity is specified by the Association of American Railroads (AAR) Standards. For example, these draft gear assemblies have a specified capacity of at least 36,000 foot pounds. Further, it is important to note that the action of the friction clutch system enables this capacity to be accomplished without exceeding a 500,000 pound reaction pressure being exerted on the center sill member of a railway car during make-up and operation of a train consist. This maximum reaction pressure is required so that these high energy shocks can be readily handled without upsetting the shank of the coupling member and/or damaging other critical car components and cargo.
It is also well known that as wear of the friction clutch components occurs in these draft gear assemblies, efficiency of the draft gear assembly, during the initial application of a force being applied thereto, is diminished. Further, this wear of the friction clutch components generally results in a more non uniform operation of the draft gear assembly.